qemu: snapshot: Reject internal active snapshot without memory state

A internal snapshot of a active VM with the memory snapshot disabled
explicitly would actually still take the memory snapshot. Reject it
explicitly.

Before:
 $ virsh snapshot-create-as --domain VM --diskspec vda,snapshot=internal --memspec snapshot=no
 Domain snapshot 1401353155 created

After:
 $ virsh snapshot-create-as --domain VM --diskspec vda,snapshot=internal --memspec snapshot=no
 error: Operation not supported: internal snapshot of a running VM must include the memory state

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1083345

src/qemu/qemu_driver.c

@@ -13495,6 +13495,15 @@ qemuDomainSnapshotCreateXML(virDomainPtr domain,
             align_match = false;
         } else {
             def->state = virDomainObjGetState(vm, NULL);
+
+            if (virDomainObjIsActive(vm) &&
+                def->memory == VIR_DOMAIN_SNAPSHOT_LOCATION_NONE) {
+                virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
+                               _("internal snapshot of a running VM "
+                                 "must include the memory state"));
+                goto cleanup;
+            }
+
             def->memory = (def->state == VIR_DOMAIN_SHUTOFF ?
                            VIR_DOMAIN_SNAPSHOT_LOCATION_NONE :
                            VIR_DOMAIN_SNAPSHOT_LOCATION_INTERNAL);